I’ve found that the Tempest’s output is just fine for plugging directly into the Rytm, which can’t be said for all instruments. The Electribe2 struggles with this, as does the Volcas (obviously) and so on.
The Tempest, however, is more sensitive to volume control than many other instruments. Take it down too much, and it loses a lot of the details in the modulations. Pick it up, and it can get too loud and just eat up space in the mix. In general, it’s a hard instrument to tame, and I don’t think it just comes down to skill. Compared to Elektron’s instruments, it’s not all that balanced in what it puts out, thus the individual outs where you have more control over each voice. So this is always a bit of a challenge when using it in the Rytm’s input, which is weak to begin with. But the sweet spot is there without compromising too much on the Rytm’s internal track volumes, as opposed to using for example a Volca Sample, which is almost hopeless without some kind of amplifier in between.
Anyway, once the Tempest is in the Rytm and you got your levels sorted, it works quite well together with the Rytm. I don’t much use the Tempest compression when I plug it into the Rytm, since the Rytm’s is just better (in my ears, at least), but I frequently use the Tempest dist. It’s raw, crude and gives the sound a very unique flavour.