Are there any particular recommended flags for either the ATI 4830 or 5750 under guiminer? I don't intend to overclock either of them so as to not lower their life expectancy too much.
Also if possible could someone explain what the flags do? (ie. "-v", "-w128", "-k", etc.)
(The guiminer readme is available here: https://github.com/Kiv/poclbm
-v enables vectors, which is faster on some cards.
-w is for worksize, and varies by card.
In general, you should look at the flags listed for the highest performing entry for your card on the wiki here: https://en.bitcoin.it/wiki/Mining_hardware_comparison
where it appears that "-v -w 128" yields good performance on a 5750.