PT9 is not hardware tied anymore, and runs on/with anything, yes.
Though the only reason I can think of to buy it is to tell my clients "I use PRO TOOLS", stick my chest out and let them think that their mixes were made with pixie dust and unicorn hair. I have no time for such nonsense. DAW choice comes down to three things:
1: Can it do the basic stuff you need it to? Edit, mix, implement midi, buss, yada yada in a fashion that suits you and to the degree you need it?
2: Will it run everything you want it to run, VST wise?
3: Workflow. Can and do you get along with how you do each thing you do in the VST, mechanistically, and does it integrate with the rest of what youre doing well (tracking, triggering, blah, sampling, blah blah, running outboard effects/mixers, integrate with/working alongside other pieces of software, blah blah blah).
Nad; try increasing the buffer size. 128 and 256 are common defaults, and you need it to be low for tracking (I've taken to tracking @96, 24, 48 bit buffer: 0.9ms in, 1.5 out, sweeeeeet) but you dont need low latency for mixing, just ramp up the buffer and see if its more stable/less strenuous on the machine.