Most LC475/Quadra 605 machines use a pre-Intel CPU, which will make any video encoding painfully slow; at the very least get a machine with an Intel CPU, if you want to encode vide…
I would not "practice" on a IIx board, they are kind of rare. The IIx was not out very long before the IIfx came out and many of the II and IIx systems were upgraded to IIfx boards…