A few remarks on different RME interface options, hoping to clarify a few things for you
1. RME UC (875 Euros)
This interface hit the market 10 years ago and it doesn't have TotalMix FX, it only has the regular TotalMix. This means, you don't have EQ, Dynamics, Reverb, Delay, you can't use the TotalMix Remote app and it doesn't have direct connection of the great ARC USB remote control either.
2. RME UCX (1169 Euros)
This interface hit the market 7 years ago and it comes with TotalMix FX including all 4 DSP effects categories mentioned above. It should (haven't tried) work with the TotalMix Remote app. It still doesn't have the ARC USB direct connection though.
3. RME Babyface Pro (689 Euros)
This interface hit the market 4 years ago and it comes with TotalMix FX, includes EQ, Reverb, Delay but lacks the Dynamics! Also, it doesn't have coax S/PDIF but you can extend the inputs via optical ADAT. No connection for the ARC USB though but this interface has it basically built-in. TotalMix Remote app should work.
4. RME UFX II (1999 Euros)
This interface hit the market 2 years ago and features all of the current bells and whistles … but as mentioned before, it doesn't have coax S/PDIF. The even more expensive UFX+ is basically the same interface with the added MADI.
Even if it sounds a bit frustrating, the above mentioned 4 options are the affordable options from RME. Everything beyond gets really expensive due to the additional infrastructure required to leverage the massive potential.
One remark regarding the onboard DSP effects. By default, these effects are only used for monitoring and will not be recorded. It can be changed but this doesn't make much sense. Here's why I really like to have the DSP effects:
1. When I record vocals, it's nice to add a touch of compression and EQ and maybe a touch of reverb to the vocalist's headphones. Makes him/her feel a bit more comfortable as opposed to totally dry. But I don't want to record it "wet".
2. I use the EQ quite a lot when recording bands playing "live" in the studio. Still I don't want to actually record "wet" but it helps a LOT for the monitor mixes. Dynamics I typically use for bass and vocals (again, monitoring only).
TotalMix FX is a breeze to work with, can be remote controlled in many ways. It requires quite a bit of screen estate to have everything accessible but I wouldn't want it to be any different.
If you're not running a studio and just record yourself, most of the "fancy" stuff won't matter much to you. Even the latency topic doesn't matter at all when you record guitar, vocals, etc. and use direct monitoring which all modern interfaces offer. Latency and buffer settings only matter when you play virtual instruments via MIDI keyboard or by using eDrums.
If you're on a tight budget, go for any of the Focusrite USB interfaces like the Scarlett 18i20 2nd gen or the Clarett 8pre USB (better preamps). They are good value for money, no doubt. And for a small, personal home studio they do the job really well.
Hope, my novel helps
Martin