but if I recall correctly, didn't the USSR had to do massive purges because a nazi wing of government that wanted to overthrow everything was forming and getting into crucial positions of power though?

There was the initial purge of government and then there was the purge of the military a little bit before ww2. The thing is, the purges worked to prevent reactionary elements for a while, and then 1/6 of all Soviets died defeating fascism and you lost basically two generations of the most ardent communists and the government got taken over by reformists. I don't think a decentralized system would have worked better, using the Spanish Civil War as an example.

as for the question I'm not really sure, I don't think any amount is going to make the fascists "bend the knee", I honestly think it'd be better to just exile them

I mean exile is basically the death penalty. I dont see how you can oppose forcing them to do things for their own good and support just killing them.

i think people less extremely against the new systems should for the most part be more open to collaborate if they find out they have an actual, tangible and real say in things, forcing may have the opposite effect

There were soviet forced labor camps whos entire purpose was to demonstrate to reactionaries the new, collaborative way of working. They were paid a good wage and not alienated from their labor like under capitalism, and they could go into town, visit family, etc so long as they kept showing up and doing what needed to be done. The entire point was to forcefully show them the advantages to them of the changes in society.