I use a flickerfixer with my A1200 and have OS3.9 installed. Standard resolution I use is high-res interlaced with maximum overscan (something like 724x566 pixels or so) and it works great. The monitor I use is a 15" Compaq CRT and the image is very crisp, although you have to keep in mind the refreshrate is 'only' 50 Hz and therefor you will keep a slight flicker.
Anyway, if you want to keep your A1200 in its standard casing (like I do), you can either use the standard 1084 with a maximum usable resolution of 640x256 or you can go for a scandoubler (preferably with builtin flickerfixer) and use a 'normal' more recent monitor.
If you want to go for an LCD-screen, check if the screen you want is usable with your Amiga. Many LCD-screens cannot handle the Amiga's 50Hz signal very well and will give a distorted result on your screen.
Oh, btw, if you want to look for a turbocard for the trapdoorexpansionslot of your A1200: the Blizzard 1260 (with an optional SCSI-hostadapter) is, and will most likely remain, the best card you can fit in a non-towerized A1200. No, I will not sell mine... ;-)
The choice between a card with a 68030 or a 68060 not only depends on the speeddifference, but also on what you want to do with your A1200. The 68060 is less compatible, but much faster compared to an 68030.
