Unfortunately I mainly use T3 for parking: nearly always fly out of T4.

Checking curbside, at some carriers you can watch your bag x-rayed but I haven't had one opened up there for a long time. The operators occasionally seem disconcerted to notice they're being watched, but I haven't been told to "move along" in ages. Occasionally they even ask why. When I explain about grandma's rosemaling TP holder/my sophomore textbooks, they treat it gently or even bring it over for me to verify locks/ties intact. The breaking in and pawing through happens later after it goes below. Maybe they mark it or something.

Inside: at major carriers you self-check, watch an agent wrap the bag tags on and haul it to the conveyor belt. Forget if BA still have theirs right out next to the class-segregated lines. Again, I never see it opened there.

T2 has had exceptionally arrogant, ill-informed screeners and barkers: I avoid it now. At one time TSOs were trained there, it was a zoo. T4 has its share of barkers and little emperors but many seem to be taking hints lately to smile more and use their indoor voices. High tourist days stress them out.

Good luck at T4 when you go. The new passenger level has lovely tile, art installations, and fine retail opportunity. Handles noise competently. That's the terminal I meet people if there's some kind of long wait. Not a bad place to hang out if you forget your worldly goods are being ravaged four floors below.