Mountain maple is the generic Japanese term for all Acer palmatum, Japanese maples. There are also many different cultivars of JM with different shaped and colored leaves. This appears to be one of the bronze leaf/ red leaf types so the leaf color is natural for it in summer. They do tend to have larger leaves than some other cultivars which can make smaller bonsai more difficult to achieve.
Burnt leaf edges is par for the course on JM. Plenty of water should reduce the extent. They can be defoliated in late summer in time to grow a new set of unmarked leaves for better autumn colour but that's really an advanced technique for established trees. Younger, smaller trees need all the leaves they have to grow and stay healthy.
Best location depends on how hot the sun is. Full sun is better for compact growth but if leaf burn continues try to provide some afternoon shade. When daytime temps get near 40C here I provide shade.
This tree is fine for a beginning tree.
JM have a tendency to develop lumpy areas when a cluster of shoots grows from one place. The cluster at the top of your tree is typical. When you see more than 2 shoots at any place they should be thinned to avoid lumpy growth.
Thanks for the info Re cultivars, makes a lot of sense! I suspect you're right, that it's likely a red leaf cultivar. I'm guessing observing the colour changes throughout the year will make that clearer!
Yeah I read about defoliation, but I agree it's not something I would try yet, good to keep in mind for future years though. We had temperatures of 35C recently, but that's very rare in my parts, will keep an eye on it though.
Thanks for the cluster info, actually one step ahead on that part (for once!) - removed down to two shoots last night. Good to see I'm learning something!
Like I said, I'd have been quite happy just enjoying this tree, not treating it as bonsai. I'll see how it gets on over the next year
Thanks for your great info, as always!