Use excessive amounts of wall grates is my design tip, and purposely use single tile retractable bridges as stopping plugs over instead floodgates because you can blend them into the floor, and in a emergency retract them onto a layer with exposed pools of aquifers to drain
++B++
B
+A+A+
(Same as the key in the diagram below, but A is exposed aquifers)
Also works as decorative pillars for traps, should you want to flood someone (or alternatively put out fires/irrigate but you dont want to have to cut a hole or put down a floodgate)
Obsidianising plug - Bridge drops water that should disperse to 7/7 in the room or otherwise covers a bordering aquifer wall of that height of 1 z level, while the screw pump above it pushes magma ontop of the 7/7, a emergency water valve above can remove spare magma and you can dig away at the obsidian at your leisure.
WWWWWWWW
+0+++H++
+B
SB
+B
(W is water, 0 is the hole between the bridge, B is the bridge, + are solid tiles and S is the screw pump)
I like to put wall grates everywhere, because they can be seen though and are basically cheaper and more aesthetically pleasing iron prison bars (which really need more love) they make great animal containment, Z level pit containment (as long as no item breakers are present they cannot be escaped out of) for cage matches and impromptu zoos and functional windows for areas like training grounds which i put opposite my entrances and important areas so dwarves always maintain a line of sight with the enemy and can pull themselves off whatever task to go fight.
Doors have to be put against wall tiles, but wall grates can go wherever, so go ham (3 wide entrances with 2 doors and one grate between works well enough)