I've got a Ryobi One+ 165mm circular saw and I find it does the job of light trimming very well. It is easy to manoeuvre, light and doesn't scare me like larger more powerful models can. If you are planning on cutting mainly plywood, trimming up to 19mm thick boards or cutting 45mm thick timber to a length I would highly recommend it. If you are considering ripping 45mm thick timber down the full length at speed I would stick to a plugin version or opt for the Ryobi one 18V Brushless Circular Saw Skin Only. In saying that it is a great trim saw and suits its purpose perfectly.
Although this machine can cut these different materials I would advise cleaning out the machine if switching from timber to steel. You'll need to clean any remaining timber residue out of the guards and collection area and remove the collector whilst cutting metal.
Depending on what work you will be doing on acrylic or metal sheets you might wish to consider a jigsaw. Although not as fast at cutting as a circular saw, they are comparably more versatile allowing you to cut fine details and shapes. A multitude of different blades can be purchased to suit just about all your cutting needs.
A jigsaw is very slow cutting compared to a circular saw and can only cut thin steel. A circular saw will do wood and acrylic, though you will be better off getting different blades for each task and also to put masking tape where you are going to cut acrylic as it makes a better cut. With cutting steel, an angle grinder will do that job better. Brand isn't really a big thing with most tools, it all comes down to your budget. - Razzer