Am i right in thinking if you have a premium account and you attack someone or they attack you, you can see their weapons and stats like you can if you pay 50 credits to spy somebody?

Yes, you can see the stats and weapons after the attack in the Backstab History.

after the attack?

Yes, after the attack.

This feature is only for Premium account.
First, go to premium's tab --> select Backstab history --> you can click to choose from a list of attack that being done by you or by others excluded the alliance attack.