AFAIK, you should switch to Asio4all in the host program's audio device setup. I unfortunately cannot help you find that in VSThost since I have not used it myself.
In reaper, is your problem that Reaper does not show any of the VSTs or that they don't work? It could be that the VST folder has not been set (it's the one where the program searches for any VST intstruments/effects on the computer). You can find this in Reaper from Options->preferences->plugins->VST and then selecting the plug-in path*.
Regarding asio in reaper, you can find the driver and latency settings in Options->preferences->Audio-> device. Select ASIO and try what happens. There's probably a asio configuration setting in the same page, which has latencies/buffers listed for selection.
Hope this helps,
*vsts are .dll files, and they're often installed to the same folder, like Reaper\plugins, or the like. In this case, it could be that they are in separate folders created by the VSTs you have installed. You can add all of them separately as plug-in paths in reaper if you want to.