as im a newb still,
heres from my point of view:
semi-speed - usually using power/sprint dash. typically minimum of 3 straights after a jump/slope.
semi-tech - usually using LD/TT/AT. typically 1 straight after a jump/slope. more to technical side like, bank - bank - single jump - bank or slope/jump - corner.
as for speed. no jump, no LC. just rainbow, straight and corners. typicaly using sprint or macdash.
speed-tech - errr never experience it before. lol.
thats it from a newbie like me.
perhaps more experienced and seasoned player will xplain further. haha.

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semi-speed layout

semi-tech layout
still searching
speed layout

p/s: i duno how to explain. rofl.