DSPs and Routing them in hardware or software

I immensely appreciate it if someone can help me with my questions.

I have a MOTIF XF with its FW16e audio interface (firewire) which sends out 2 master channels and 14 sub-channels to the PC (also has 6 channels back). I’d like to purchase either a UR242 or UR44 unit to use their effects processing capability as well as the extra inputs/outputs. My questions are:

1-Is it possible to route the master channel of fw16e to two of UR242/UR44 from a DAW and take advantage of the DSP effects processor in them?
2- Is it possible to route channel 1 and 2 on UR242/UR44 to channel 3 and 4 like a chain and use the DSP(compressor mainly) only on 3 and 4 for example?
3-If 3 is not possible, is there a hardware compressor effect to apply to the master output in UR242/UR44?
4-How efficient is the above-mentioned approach compared to applying the effects just by using Logic’s software AU plugins?

FW16e is a good audio interface here is the latency I get in Cubase AI 6, with my old laptop:
Buffer size 128: I:3.991 O:3.628
Can Steinberg UR242/UR44 outperform it?