As explained here, as well as countless other reasons, I’d pick HSMAdvisor over GWizard any day. However, Kennametal’s NOVO calculator is free and likely more accurate than anything else when milling metals with their reasonably priced material specific endmills. But, like with GWizard, you have to divide the cutting torque by the cutter radius to get cutting force.
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Not arguing, just saying I like it, and for the others, including @Kai , who the reply was to, just wanted to mention there were other tools to help with HSM on small machines.
You asked about reasonably-priced thread mills. I find Rogue Systems Inc. on eBay to provide them for good prices. Roughly $22 for any threadmill. https://www.ebay.com/itm/254610651598
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Or, direct, https://www.carbidetoolsource.com/
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Thanks guys, these are both cheaper and a lot faster to get than the ones I got previously on AliExpress.
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Just to add a little more complexity, how are people calculating their cutting parameters for contouring 3d surfaces w/ ball end mills. It’s no longer as clear cut as DOC and WOC when you have a spherical cutter. Depending on how steep or shallow the surface is, the part of the cutter which is engaged changes (affecting surface speed) as well as how much it’s engaged (not sure if this is accounted for in Fusion 360’s CAM or not).
Here’s an example of a part I machined in 7075. I would like to think I could achieve better surface finish, but again I’m not sure if my expectations are just too high for a kit based router. Luckily the surface is completely non function and was just a chance to try out something new, but in the future I could foresee wanting to create conical or spherical surfaces with nice surface finish without having to buy a lathe (or for parts too large to fit on a lathe, e.g. 3-pc wheel centers).
0.2mm stock was left before this operation and I used a scallop w/ a 0.2mm stepover w/ a 1/4" 2 flute uncoated carbide ball end mill.
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Have a look at NYCNC’s video with some info on ball end mill engagement calculations for propper SFM.
"carbide cutting tools CNC ground in the USA just a stone’s throw from the world famous Rogue River." World famous for catching on fire! 
Carbide Depot sells “pro grade” stuff at reasonable prices and has useful technical resources.
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To get the best 3d surface finish you might want to try a single flute ball endmill. Datron and 2L inc make them as far as I know. A single flute will minimize the effects of runnout and machine force.
I’m my early days with billet intercooler endtanks it became painfully obvious how direction, stock to leave after roughing, and engagement angles work.
Try bumping stock to leave to 0.5mm and run toolpaths where the side will engage before the bottom. You need enough stock to create enough tool pressure to stabilize the cut. Depending on part geometry, bottom to top is usually the best bet.
Your tolerance and smoothing options will greatly effect the finish especially when feed speeds are higher.
Checkout this set of calculators
https://www.iscar.com/ita/Calculators.aspx?units=M#
Pro tip - match chipload with stepover to create the best finish.
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