I've personally never needed a kickstart switcher. I also think an indivision ECS is more value for money than a subway. On A600, pcmcia is totally adequate for file tranfer so flash sticks are not a big advantage and games cannot use USB mouse/joypads so you'll still need to keep original type mouse/joystick around anyway. IMO, you get much more advantage from being able to use a modern display.
Subways are sold out too and apparently not likely to get made again soon. Also A603 is replaced with A604 1MB expansion.
As for web browsing, it is worth setting up, mainly for "because you can" entertainment value but if a site isn't loaded with modern features, it is reasonable to use, notably, aminet.net and eabmobile.abime.net. It is slow on ACA630 though, might just be unbearably so on the ACA020. For choosing an OS, have you seen classicWB. You need a set of WB disks then these packages add on a host of useful stuff. http://classicwb.abime.net/