With the sucky 23-25W PSU that comes with the A1200 you risk killing it just attaching extra diskdrives so for love of god at least get hold of an A500 PSU that gives twise the power. No matter what ppl tell you the PSU will not stand it for longer times... I actually killed an A500 PSU after about a years usage by hooking it up to my A1200 w. B1230, 3.5" HD and 2 External floppys so. (also my A1200 w. B1260, 3.5" HD, 1 External floppy, Scandoubler, PCMCIA Ethernet and Glowwhire didn't even light up with an A500 PSU).
Generaly speaking 030 cards go between 7-11Mips, 040 cards between 18-35Mips and 060 cards at 80+Mips. 030 cards are by far the best compatibility with 060 coming second and 040 last.
030 turbocards can easily be placed under the lid of the trapdoor and should be safe, though cutting air holes and perhaps even adding a heatsink doo prolong the CPU's life. 040 Gets very hot and isn't recomended for the A1200 though with heatsink, fans, no trapdoor cover and feets to lift up the machine it can work (I know... my BPPC040 looked like that in it's pre A1200T era). 060 cards though they usually don't come with any cooling are very happy to at least get a heatsink (and fan if you intend to overclock it) and above mentioned cutout of the trapdoor should do just fine.