Casting through allies

[fjmyth]

New PF2e player here. A lot of googling but I can't seem to find a clear answer to what spells, if any, can be cast through allies. I read up on the Line of Effect and Line of Sight which seem to indicate as long as there is a 1 foot gap then you have both. Also there is the bit about "Line" area effect of spells taking up the full 5 feet. Does this mean that any spell which doesn't specifically state something like "Area 120-foot line" like Lightning Bolt can be cast through allies space without penalty? Fay of Frost for example could be cast at an enemy with one or more allies standing directly between the caster and the target? Thanks!

[Losonti]

Lightning Bolt is, barring unusual circumstances, not stopped by creatures, otherwise it would be a very poor AoE spell. For spells like Ray of Frost, though, because they involve an attack roll against a target's AC, any creatures between the attacker and their target would provide lesser cover to the target. Lesser cover provides a +1 circumstance bonus to AC (but not to Stealth or Reflex saves, like standard and greater cover).

[aobst128]

For line spells like lightning bolt, allies are effected if they're in the line. For spell attack rolls, if an ally is in the line of sight, it grants the target lesser cover. +1 to ac.