It is no problem at all to run a UR44 on a Mac. I'm using it on a MacBook Pro.
You are also able to use all the DSP features coming with the UR44 together with Logic or any other DAW.
Unfortunately some DAW vendors do not support VST 3 as a plug-in standard. The Basic FX Suite plug-in bundle, included with the UR44 is VST 3 only. However it can be the case that these plug-ins are not supported by your DAW as native plug-ins depending on your DAW of choice.
But this is only valid for the native version of the plug-ins and only with VST-incompatible DAWs. The DSP-based plug-ins can be used via the dspMixFx application with every DAW for monitoring purpose.
Even if the name of the UR44 does not imply it, the UR44 has six inputs. Two of those are true line inputs on the rear panel.
Recently a video review of the UR44 has been released on MusoTalk, a German news and media platform for music gear. During the review they have used the UR44 with Logic.