A Plus is slightly too slow and limited for real use - they have no internal hard drive, can only read 800 kb floppies, and can only take up to 4 MB Ram, which is not enough to do much with (even running Mac OS 7.x will be a bit of a struggle on one). It is also very difficult to get one networked, and they are too slow for the web anyway. Classics are also similarly slow, although more modern than the Plus. Most people here would say an SE/30, because it is by far the most upgradeable Compact Mac (they have an expansion slot eg for a network card, and can take up to 128 MB of memory) and has the faster '030 CPU. No 68k Mac will be good for web surfing though, it is a very slow experience and the browsers that will run on them (version 4 of IE and Netscape are the newest that will run on 68ks) are not compatible with many modern websites.

Do you definitely want a Compact? For the things you say you'd like to be able to do, a desktop Mac might be a better choice, even something like a PowerPC with Mac OS 9.1. A newer Mac is also of course more likely to be in better condition, and you will most likely find one in good condition for nothing or next to nothing, whereas Compact Macs are more scarce these days.