I have RY4S plus which I really like. Worth to buy 300 ohm version ? I have Fiio M9, btr5 and sonata hd pro to drive it. It's ok for them ?
RY4S 300 ohm is drivable on sonata HD Pro, I'm not even using a 3.5 mm to 3.5 mm jack to trick it to go to a higher power output and it still sounds great. As the 300 ohm impedance suggests, it is quite power hungry, I think your BTR5 can also handle it, just don't play it from a low powered smartphone.
RY4S 300 ohm is a more refined and mature tuning of the RY4S plus 32 ohm. The 300 ohm version is more U shaped than the V shaped RY4S plus 32 ohm. The 300 ohm's subbass and bass quantity isn't as big as the RY4S plus 32 ohm but it has better bass quality (less midbass bleed, faster bass and better accuracy). The 300 ohm's lower mids ain't as recessed and the upper mids ain't as hot as the RY4S plus 32 ohm. Technicalities slightly better on the 300 ohm version too, but not as good as some midfi earbuds.
If u can wait for sales, I got my RY4S 300 ohm at $15 USD from aliexpress. Actually if the mids can be a bit more detailed and the subbass extension better, it can compete with some midfi earbuds in sound quality, but as it is 15 bucks for this kind of sound is excellent. I'll skip a restaurant meal for this for sure.