It's mostly determined by the terrain and overall grip, but I think Varg EX requires different (better) tires than the 2T/4T bike.
This is due to power delivery at low speed and low engine RPM. At higher speed, on compact terrain with decent grip it doesn't matter that much.
On steep inclines with loose rocks it matters a great deal more.
It could all be solved with clever traction control, but it seems we're not close to that.
So far I had:
- Stock Metezeler 6 days: Ok-ish until 50% of wear but after that almost no traction in tricky spots.
- Mitas Terra Force EF Super (yellow): Very similar to the Metzeler, perhaps a little worse. Both will lose traction easily. I had more wheel spin on the Varg in one ride than in years on the 2T bike.
- Mitas Terra Force EX MH Soft (green): Only one ride, and it's a 110/100. Every new tire is good, so I'm reserving judgment for now.
That's supposed to be a "replacement" for the XT 454 mentioned above. It's not too soft. Be careful in following the sales blurb of "soft, hard, gummy ". It's gotten so bad that even the manufactures don't know what it means, and I have that on good authority. Best you can do is test one or two tires and stick with what works.
(F.U. Mitas for your nomenclature that changes every year 
)
For the front I have no complaint and I'm still using the stock tire with most of the life still in it. I remember preferring Mitas C-19 (now EF/EX) front tire to the Micheline Enduro. I know it well and it works almost everywhere.
It's all about rear traction. Varg power output from 0 to 1/4 throttle is the same at 20-30-40-50-60PH. You just need to open the throttle more on lower HP.
If you're a flat earther riding on soil, sand or mud my opinion isn't much use. All I know is rocky hills.
