Ok well, I wouldn't be too worried because it's about the norm these days for 2 phase closed loop motors. However, what I would say is pay attention to the Max voltage because if you want the best performance you want higher voltage and these drives look like the say Max 50V.

If you want 5.5Nm and speed then you'll want to run them at least 65Vdc so look for drives with max voltage 80Vdc. Also, lots of drives now come with option to use AC or DC voltage and AC option lowers the cost and complexity because you don't need to build a DC PSU so can get rid of capacitors and bridge rectifier from the costs.

Regards Tuning and controller compatibility then provided your controller uses Step + Dir then they will work with any controller and tuning is simple, often they are self-tuning and you just select the micro-step level.

I've fitted 100's of similar motors/drives and you won't have any issues with setting them up and they are very reliable. THE most important thing is you don't run them with too high a voltage, so whatever the drive Max rating use a PSU at least 10% lower. If not you'll blow them up and this applies to any Stepper/Drive not just these or closed loop.

Lastly, remember you will pay the VAT and Admin fee when they arrive, also I think you'll find the cost of shipping is quite high at the minute so the cost will rise.