Hi,
welcome to the RME user forum.

Depends also on
- how well drivers are written
- for USB, e.g. which transfer mode is being used
- RME does communication with PC through their own FPGA, not using 3rd party USB/FW/TB chips
- how quick the A/D and D/A converters are

Here RTL (round trip time (A/D, transmission to PC, back, D/A) of different RME interfaces from my blog article about UFX+
https://www.tonstudio-forum.de/attachme … es-v2-jpg/

1 no
2 yes, then most.
Roundtrip latency can only be measured to be sure and know what is really happening.

And honesty! Many companies give semi false buffer sizes. Yes seen from the daw the buffer is for example 256 samples. But in reality it uses double or triple buffers or a very large safety extra buffer. (RME uses a small safety buffer too, but it is very small, if I remeber correctly 32 samples and reported to the daw by the driver)
And even if true buffer size is given, what use it it to have for example a 64 buffer when it gives only crackles and you have to use 512. Plus cpu usage can also be higher then RME. If only things were simple...Of course there are other good companies but also mediocre and really bad. Also it can vary from device to device from the same vendor.
But in the years I use computer audio, nothing has performed better for me then RME (I am on windows)

BTW this is not just my opinion, but investigated by Tafkat  the maker of DAWbench, that is still used today, if the dawbench forum and papers are still available it is a very good read if you are interested.

Tribute to your opinions
I really appreciate it.

And let me tell about my cases that I'm suffering

I had a problem for using my desktop as a music production.

I do many things by myself from instruments to mixing.
And the biggest thing is that I need decent environment to play the live session (I'm streaming my music live on twitch)
So I need as low latency as I can. But I always hear some click/pop noises during the live. (mostly set on 128~256 samples)
but I think my PC is sufficient for playing performances. (Ryzen 2600x / 32G RAM / some SSDs)

So I did a test yesterday, and I can catch that the noise are even caught in the empty project(using 1 mic, 256samples)
Got frustrated, and kept trying to find the reason.

And today I shifted the usb port of PC connected with audio interface, and it's optimized! (but also has some probs on 64samples, maybe 64samples is pretty intensive to my CPU)

but I'm still wondering that I can't play the live performances on 64samples with my PC.
If I can what should I check for?

----i'm using ufx+----