Media Size & Custom Image Size Questions

[Catherine_B]

I can't find the answer to this exactly.

I read the media settings tutorial. In it, default settings are 150 x 100, small, medium setting 300 x 200, large 600x400.

I'm unaware where 300x200 is being used in Agent. Is there any reason not to set it at 150x150, so as not to have to manually make those images for the lightbox images?

When I uploaded a larger image than 600x400 then clicked on that radio button to insert it as 600x400, it did not resize down. Should it have?

Also - I thought the FCG was supposed to ideally be set at 600x400. Today I'm noticing that most people who submit their own sites in the help section seem to be using a smaller size, including the demo (I don't know how I missed that).

Are my pictures way too big? That might be part of my loading time issues. What is the large size most people are using, please?

Thank you in advance from Catherine.