The maximum size actual content you can put on a 700MB (80 min) without overburning is approx. 702-703 MB.
There's no practical limit to how many times you can have a link to the same file in an "optimized" image you burn to a CD, if you need to do that for some reason. I have just burned an 18GB image that only uses approx. 3.5GB space onto a 4.38GB DVD, where each file is linked up to 16 times (consolidated weekly backups over 16 weeks plus some additional stuff).
If you use UltraISO to make the ISO image before burning, you check the "Optimize" option in the File => Properties... menu after having opened the image.
There's also a similar "Optimise Duplicate Files" option in ImgBurn 18.104.22.168 that I haven't tried yet. It's in the Settings dialog on the Build tab.
VCDs are burned on CD-R in Mode 2 Form 2 which has less error correction info than the usual Mode 1 or Mode 2 Form 1 formates used for data, so you get 2352 bytes instead of 2048 bytes in every sector, which is approx. 806 MB on an 80min CD-R or 14.8% additional space.