Vart the Fire Man's page

I've done my best to comb through the rulebook and tried searching for an answer in threads on this forum but so far I've come up with nothing. I apologize if I'm just blind.

Is something like Total Cover gone in PF 2.0?

I understand that cover still exists, and as per the rulebook "To determine whether a target has cover from an attack, the attacking creature or object draws a line from the center of its space to the center of the target's space. If that Line passes through any blocking terrain, the target has cover."

I've tried to find 'blocking terrain' and there's nothing. Under Line of Effect there are a few pertinent rules but they seem focused on spells, and I can't find any links anywhere else to ranged attacks.

So my question would be: What, as per RAW, prevents a PC from shooting through a house to hit a target on the other side?

I've been tossing around ideas for awhile now on what might be done to help alleviate some of the issues with high level gameplay (in this case level 13+). I've read a fair amount of creative ideas on fixing the problem, as well as definitions and redefinitions on what the problem actually IS, and that has led me to my current question:

Would limiting the highest spell level available to spellcasters but keeping the spell slots for those levels help to balance out higher level gameplay?

I most often see people point to the 'broken' spells as being the main reason casters start to truly overshadow the other classes past level 10. What would happen if full spellcasters never gained access to level 7 spells or higher? Partial casters no higher than 4th? Limited no higher than 2nd? They would still gain those spell slots - to be filled with lower level spells or metamagic versions, but the most powerful spells of 3.5 and Pathfinder would be gone.

Would this have any effect at all? Is 6th level spells already high enough to make casters gods?

What do you think?