There's no capping on points transfer.
For charges, it all depends on the program you transfer points to. You'll have to check individually for every partner program and also specific redemptions.
Some partner airlines flight redemptions have very very high surcharges others almost nil. It also depends whether you book flights in their own aircraft or partner airlines. In some cases these charges can even vary depending on the airport you're flying to/from.
For most you'll have to pay taxes on the tickets and often there will be some additional charges involved.
For hotels it's about the same.