well just been looking into this on another thread.
for the free stuff - it looks like a pronterface & slic3r combo is probably the best control & print option around.
I - personally - recommend simplify3d. No it's not free, but it is extremely good and I don't regret buying it :-)

That said there are a bunch of free internet based slicers around. My internet is dicey at best (i'm almost the last house on the local telephone exchange) and my wifi in my workshop is also a tad dodgy, so I don't do cloud/internet based software.
Plus I simply don't like the idea of it anyway :-)

Here's a list of some of the ones I either haven't tried - or might have tried a few years ago when they didn't really work and I hadn't bought simplify3d :-)
https://all3dp.com/1/best-3d-slicer-...re-3d-printer/