Hello,
To my knowledge different Fablabs have different rules for how many different types of MOSFETs you can use in a single chip (Low Vth or High Vth or Ultra Low Vth or normal).
for digital circuits for example
non critical path could use High Vth to decrease the leakage current thus overall power drops.
while critical paths would use a Low Vth for faster speeds.
in analog design, Low Vth is suitable for low voltage applications without sacrificing speed
on the other hand if there is a power constrain on a certain block you could use High Vth to ensure that block operates in subthreshold however on the expense of a much smaller bandwidth of course.
hope this helps.