I recommend cutting in foam before letting the chips fly in real wood. Once you have tolerances and everything tuned on the cheap stuff, step up to plywood with confidence. Mind your feeds and speeds, know what works on your individual machine, use others' reports as a starting point to work up to.

Downcut will splinter the bottom and leave the top practically finished.

I use 0.125in with a 0.25in shank, two flute. I clean out pockets. tabs can be a pain - the more inserts, the more post processing.

I used corner radius endmill on similar finish to shooter lane with success in the past, fewer passes than ball (some would argue the scalloping could be beneficial) and less post-processing required in my use case.

I've heard less tearout or other potential issues when encountering voids in ply (assuming you have big box store crap like I do). the scallop left behind allows for more tool engagement on finishing passes. would probably be faster from rough to finish. but the scallop is just a byproduct of the benefits of a ball mill, speed and durability, maybe I worded what I wanted to say wrong.

the ball end mill is probably the tool of choice when doing relief work or free form curves. ball end mills should allow higher feed rates and the durability of the cutting edge is very high. though the only flats I've broken were from dropping them from 5ft onto the concrete floor.

Witness!