I would highly recommend the Korg Kontrol, either the K49 or the Micro version. Both work amazing well with Reason. All the different instruments are mapped to the keyboard, you can switch between racks and use transport controls (play, record, rewind).
You shouldn't have problems with latency (assuming you have a relatively good computer/laptop) as Reason is very light on the CPU. It still runs fine on my 4 year old laptop.
If you're using Reason with other software (Cubase/Ableton etc), or recording audio in with Reason 6, you may need an external sound card. There are tons to choose from depending on your needs - you could take a look at Propellerhead's own 'Balance' hardware.
VSTs don't run with Reason, so you won't need to bother with them. There is a product called Receptor which is a hardware VST player, which you could use with Ableton/Cubase etc, but not with Reason.
Reason has no MIDI out, which means you can;t send midi signals through it to external kit.