There are many areas of open plain and undulating hills. I'll take your word that there being hillier, rockier and more vegetated areas that are unsuitable for an amoured push but it isn't the west of Afrin with an ATGM possibly positioned behind any one of a hundred million large hillside rocks and olive trees.
With appropriate air and infantry support, armored divisions could move through much of the North in my uninformed opinion noting the key towns along the border are low lying fruit as far as targets are concerned.
Trump's generals will need to spread their troops around the perimeter and cease information sharing ..... but will they? If US troops were hit my Turkish fire Trump's red neck supporters will absolutely demand bloody retribution at any cost. They are not fence sitting Obama supporters. Erdogan may not understand the depth here.
As I keep saying it's time for China to offer a facilitated discussion table that excludes all the foreign belligerents, proxy Syrians and warlords. My understanding is that much of the YPG would join an inclusive Syrian army on condition that most civil functions are managed on a regional basis.
