You can go ZC, B16a or B18 I would go H22 in a CRX.
If you want more power just go boosted.

The ZC is cheeper and drops right in.

the B16A and B18 require much more work.
If you go with the B16 go with the B16A SiR gen 1
from the SiR EF8/9 in japan.

Im sure there is over 50 people on here who would be willing to give you the exact bake down of what each entales I would read the fourm see what issues people have had. Read about the ZC swap read about the B16A swap read about the B18 swap.

I went with the B16A in a 90HF because Im going for a EF8 SiR from bumper to bumper what I can get still keeping a left hand drive.

Either way do your homework read all you can about which ever you choose to do then read some more.
It will be expensive either way you figure about 1500-2000 for the 90 HF if you want a decient one then about 1500-1900+ shipping for the B16A(tran,ecu etc) then 300 or so for motor mounts, 150 or so for shift linkage, another 1000+ for parts you have to change all your plugs, wires, oil belts etc. you will be looking at close to 5k when you are done just for the basics. (you could also order an SiR EF8/9 front cut from japan) there are pleanty of people who do it.