concentrated fire,commando are a no brainer,ambush is good too if you can get it get it
for metathermics the damage will be too low to substiute for grenades
all feats other than cryogenic induction is mediocore,you do need a high damage to proc cryo like a shotgun or aimed shot
your main spells gonna exothermic aura,thermodynamic destabilizatio and cryostasis,cryokinesis if you want cryo to last longer
pyromyniac damage is too low and the fear effect isn't guranteed,you can throw pyrokinesis and 5/5 of the enemies will be fine with barely any damage
hypothermia con loss is underwhelming,doesn't feel strong at all
full auto is a hit or miss,you ar will at some point get so strong that a single regular burst will kill the enemy
for shotguns the best feats are sixth shell and leading shot,everything else weak compared to these 2
that's all the important bits i can think of more or less