Actually right now is a great time to get into the old school earbuds/earphones/etc. segment of the audio hobby as there's a lot of DIYers and also more traditional companies that are finally making waves about it this past 2022 year.

FiiO is also releasing the FiiO FF1 for ~$30 around September 2023, and so that's another more mainstream IEM that will be easily available on Amazon/etc. See here for more info on FiiO's lineup of products for 2023: https://www.reddit.com/r/headphones/comments/117qg60/fiios_upcoming_lineup/

For that underwater/etc. feeling, it's called the occlusion effect and so on. After a while you'll forget it exists (it's like car motion sickness, eventually you'll forget it was there in the first place), more on info on vacuum seal with ear tips, old school earphones, mini/small TWS earbuds, small IEMs (bullet style IEMs too), et cetera here: https://www.reddit.com/r/headphones/comments/zs6dpx/any_loose_ear_tips_for_iem_headphones/j182676/

Check the Earbuds Roundup thread on Head-Fi, it's the ultimate thread for earphones: https://www.head-fi.org/threads/earbuds-round-up.441400/page-4568. That's mainly where people discuss the old school earphones as a lot of people just know of IEMs (and TWS earbuds) these days.

Right now there's TGXEAR and Rikudougoku, etc. for the DIY earphones. TGXEAR probably ships from Canada, Rikudougoku from Sweden/Europe. They're often above that $20, but it's still good to read the threads and see what's available with the current (DIY + traditional IEM/earphone/etc. companies) market.

TGXear: https://www.head-fi.org/threads/tgxear-discussion-thread.964894/page-58

RikuBuds: https://www.head-fi.org/threads/rikubuds-hangout.965014/page-3. Don't forget Rikudougoku's main thread: https://www.head-fi.org/threads/rikudougokus-database-iems-earbuds-headphones-tips-ranking-list-music-list.925319/page-78

See here for more info on those old school earbuds/earphones: https://www.reddit.com/r/HeadphoneAdvice/comments/zcs559/best_wired_traditional_open_earbuds_without_a/iyyaoi3/

For the cable part, ya those are say microphonics/etc. when it's touching your shirt, arm, et cetera. It's pretty much unavoidable with certain IEMs and their cables. Like with some IEMs you can switch the cable and it may fix it. But other times it doesn't.

Some people also report static/hissing/etc. with their IEMs especially when they are not looped around the ear or like near their shirt, etc. and that problem can be solved sometimes by just getting a dongle with physical volume control if looping the cable over the ear doesn't help a lot.

Here's a bit more info on dongles (with physical volume control) and static/hissing/buzzing/et cetera: https://www.reddit.com/r/headphones/comments/117ya99/why_are_balanced_cables_so_damn_expensive/j9eib7g/ and https://www.reddit.com/r/HeadphoneAdvice/comments/100lh5a/dac_for_new_mb_asus_and_new_headphone/j2icwxm/ and https://www.reddit.com/r/HeadphoneAdvice/comments/zn88xs/help_on_iems_pc_usage/j0fns20/

Look up oratory1990 (check the subreddit, /r/oratory1990, don't forget the preset parametric EQ list (mainly for headphones but there's some IEMs there): https://www.reddit.com/r/oratory1990/wiki/index/list_of_presets) and crinacle's articles on what amps/DACs/etc. are and what they do.

Try not to wear on-ear headphones or over-ear headphones with a hat/hair/etc. on top of your head as this will tempt you to raise the volume higher. Unfortunately you just have to live with that microphonics/etc. situation with the cables or go for TWS earbuds or Bluetooth/wireless headphones.

For comfort with headphones, if you have a big head, ear piercings, glasses, et cetera, basically anything that will interfere with the seal/fit of the earpads, here's more info about headphones and glasses and workarounds it: https://www.reddit.com/r/HeadphoneAdvice/comments/zkjjcu/are_there_any_headsetsphones_that_are/j00kjt2/

With the ANC, ya I know exactly what you mean. When I first started using ANC I also had headaches/etc. but apparently this is not a normal experience for some people or they just forgot the experience of it.

For me I didn't really get pain or anything and eventually forced myself to get used to it. This was back with the way weaker/older Sennheiser/etc. ANC headphones, btw, not the newer and strong headphones from Sony/Apple/Bose/etc. that are a bit different but some people also report similar experiences when trying out ANC for the first time.

So people describe that ANC as cabin pressure, etc. And again for a lot of us it's just something we come to ignore but others say it's a major dealbreaker as yup, how can you use that feature if it's way too uncomfortable or giving actual pain.

IMO, maybe see an ENT and/or audiologist to see if you got say Eustachian Tube Dysfunction, TMJ issues, and other ear-related problems if you think it's affecting possible use with these audio stuff.

Earwax, hearing health, et cetera with Etymotics and other bullet style IEMs: https://www.reddit.com/r/HeadphoneAdvice/comments/10iwqmt/does_insertion_depth_affect_volume/j5ifw7r/

More info on headphones/IEMs and PC gaming: https://www.reddit.com/r/HeadphoneAdvice/comments/1151ezm/looking_for_1st_real_pair_of_headphones_mostly/j8zm0q8/ and https://www.reddit.com/r/headphones/comments/10zxpfb/why_are_you_using_openback_headphones_for_gaming/j85vv18/ and https://www.reddit.com/r/HeadphoneAdvice/comments/10ks4tr/looking_for_iem_for_gaming_and_music_listening/j5sjhyh/

Open back headphones noise reduction (scroll to the bottom half part of the comment), earwax clogging issue, parametric EQ, noise reduction for your PC/room, et cetera: https://www.reddit.com/r/HeadphoneAdvice/comments/115c99b/coming_from_iems_and_looking_for_headphones_150_eu/j92mpe9/

For TWS earbuds and Bluetooth usage, see here for more info: https://www.reddit.com/r/HeadphoneAdvice/comments/11565qg/need_help_buying_a_bluetooth_wireless_adapter_for/j9033u7/and https://www.reddit.com/r/HeadphoneAdvice/comments/10hdr2p/are_there_any_wireless_earbuds_witouth/j58keli/ and https://www.reddit.com/r/headphones/comments/10kai7u/should_i_keep_ear_buds_out_of_the_case_after/j5so87z/