My arrow towers are all level 7, as for the garrison i use a basic hero level 60 with skill level 3 to give me a level 2 garrison. The purple are level 80 legends with skill 3. I generally don't bother with unequipping garrisons since i wanted to train all of my heroes
I use a bit diff setup now but same concept
this layout has gotten me through F (havnt tried G yet). F is still tricky but doable, E I can farm without garrisons. Towers are lvl 9, I use TG, SM, Druid, PD, and champ or AC on hero alters usually.
What townhall are you? Would this work on a townhall 13?
im th17 (which is the lvl u get the fifth tower). I imagine it would work with 4 towers and less walls, it would just require strong enough heroes to compensate and some creative adjustments. My base is basically the clover base modified into a layout that still seperates / funnels troops, keeps heroes attacking together, and so on.
Im sure it would work with 4 towers if your heroes are strong enough.