Hello, I've had the 7Hz Salnotes Dioko since its release (I was actually part of the first ~150 or so customers that had the wrong filter problem).

You don't really need an amp/DAC, it should be fine with or without a dongle. It will require a bit more pressing up for increased volume though compared to more regular dynamic driver IEMs.

Your interface/computer/etc. should be fine. Planar IEMs are still IEMs and try not to listen too loudly as the people saying you need overkill amps are listening at hearing damage levels, lol.

Here's a bit more info on dongles (with physical volume control) and static/hissing/buzzing/et cetera: https://www.reddit.com/r/HeadphoneAdvice/comments/zn88xs/help_on_iems_pc_usage/j0fns20/

For the ear tips, people complain about (mid)bass and so use Final Audio E ear tips. Or parametric EQ. It looks like it won't fit but you just have to aim it at an angle and it'll grip just fine.

AZLA SednaEarfit XELASTECs is good when you want to make sure you have a good fit/seal but it can lower/alter the bass a lot. A lot of medical grade silicone or similar ear tips will change or lower that bass, so keep that in mind, though for me often the comfort and fit/seal is way more important than sound changes.

Try to go for AZLA SednaEarfit MAX Standard instead, it's the newer white one that was released this summer of 2022. XELASTECs are also like foam ear tips as they collect a lot of particles and stay in one shape after a while and so they're disposable, you'll need to buy new ones every several weeks or so if you constantly use the IEM.

If you think you have big ear canals, you'll probably want ear tips with the width of 13/14mm or so. But try the Spinfit offerings first.

Maybe try Spinfit W1, CP100+, FiiO HS18, etc. for fit/seal and comfort.

The dimensions/sizing/measurements/etc. for most ear tips these days will be on Amazon/AliExpress/HiFiGo/etc. But unfortunately ya you have to blind buy the ear tips in order to get a feel for the dimensions/measurement/etc. that you like for your ears. Remember, this will also change with different IEMs as they'll have different nozzle length, nozzle angle, and so on.

Here's a bit more info on ear tips: https://www.reddit.com/r/headphones/comments/zkl2fm/best_iem_tips_for_staying_put_and_isolation/j00d5yn/

Here's the reviews of someone with a lot of ear tips: https://www.audioreviews.org/guide-to-iem-silicone-eartips/

Here's the ultimate ear tip thread: https://www.head-fi.org/threads/best-iem-tips.626895/page-149

This is how you should use Etymotics or really any IEM or TWS earbud to make sure you have that good/perfect fit for that vacuum seal (necessary for the bass to be properly produced): https://www.youtube.com/watch?v=8KwXEqe6Gq4

Again for the phone it should be fine. Otherwise ya you can just get the $10 Apple dongle, it'll do the job. Better to get a well-reviewed dongle with physical volume control though as it'll be safer especially when using IEMs with PC, check the above link about dongles for more info.

Look up oratory1990 (check the subreddit, /r/oratory1990, don't forget the preset parametric EQ list: 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.

If you like a particular sound, try looking into squig.link graphs for comparisons and so on. You can try using the AutoEQ there to make IEMs/headphones sound like the others, just keep in mind that obviously it's not going to be the exact same sound.

Here's Super* Review using the new AutoEQ feature of his squig.link site: https://www.youtube.com/watch?v=RWzBw3XBn8c&t=332s

Use any EQ list or AutoEQ from squig.link as a base for your preferred taste. So like adjust the treble/bass/etc. areas if the Harman/crinacle/etc. target is still too much for you.

You can do (parametric) EQ with $8 Neutron Music Player or UAPP on Android. If on PC, the free (Peace) Equalizer APO. There are free apps on Android(/Apple) that can also do a good enough job, but most of them have those graphics sliders instead of parametric or just plug the numbers in EQ. EQ can also be used to help with channel or ear imbalances.

There's also the free Wavelet app that has the AutoEQ available now. And other free apps for more simple graphic sliders EQ, etc.