RE: Tiger 60 or 120, and what engine for each?
Check out the Super Tigre G-2300 before you make a decision. She's a 1.41 c.i. engine and a snotty one, too. $149.99 at Tower, possibly less on sale.
Next thought is how do you plan on starting a 1.20 size engine? It takes a beefy electric starter.
Lotta engine, lotta plane . . . lotta fun!