I can vouch for the cycling around Perth and Perthshire being top top notch as I'm from there! (Crieff specifically). As long as you avoid the busy A roads, it's all wonderful.
A great two day loop is Perth>Crieff>Comrie to St Fillans following the path up the River Earn to Loch Earn head where there is a good campsite and beautiful views. Then onto Lix Toll, Killin, and down Loch Tay and right to Perth. It's truly lovely riding!