For both Manly and Bondi, they're not aggressive particularly, but they are VERY VERY UNBELIEVABLY crowded!
Both beaches are often suitable for beginners but they can range from ankle high to overhead and a half (above that and they are usually maxed out). Of the two, Manly usually has the most protected and most beginner-friendly waves. And crowds. Getting out back is very simple - its usually a very short paddle.
Leaving your stuff on the beach? ABSOLUTELY NOT.
They're city beaches - full of not only surfers, but tourists, locals, westies (that's anyone not from the eastern suburbs), and that attracts thieves.
October isn't quite into "definitely warm" weather yet, but air temp likely to be in the mid-20s, and water temp should be around 19 or 20C. You will need a wetsuit, but you can probably get away with a 2mm shortie by then.
Did I mention how crowded it was going to be?
If you've got a car, head down south to Cronulla... a much more fun surfing experience, with far less crowds (not no crowds, just less crowds). Or on a small day, try Maroubra. Or head north past Dee Why.