I have the SRM-2100 which is basically same. Although it is supposed to be OK with blades, I have never been comfortable using one with a flex cable drive trimmer. For my heavy cutting I use an Olympyk 400 which is now marketed as EFCO.

For casual use like you mention, you should be OK. After all, Echo's lawyers would let them sell the machine with a hard cutting blade if they thought they'd have a products liability problem on their hands.

The SRM-210 is great with a grass blade but is short of power for brushing. Some, including Stihl, do not recommend a blade on a cable shaft trimmer. Others feel it is more forgiving than a solid shaft due to the ability to absorb shock loads.I have yet to see a shaft failure on the better quality brush cutters.Curved shaft trimmers are another story.

The 21.2cc Vortex engine on the SRM210 is a little small, Echo does not show the spec but Mantis tiller which use the same engine spec it at 0.9hp. This is a little low power. I have the HC151 which use the same engine, it feels powerful enough, but it is only a hedge trimmer.

For blade, seems like you should really get a bigger engine. 3/4" stem is not exactly small. You want the engine to last a while also, can't push it to the point of bogging!!!

Spend a little more and get a SRM260 type. You be happier. It will last a long long time.

I recently got the Echo 22 tooth brush blade for my SRM-210 and it's made a huge difference to the brush cutting performance. I was using the 80 tooth blade and this cuts small brush well but dulled quickly and took forever on saplings.
With the 22 tooth blade, it now eats anything woody up to 1-2 inches, even at half throttle. The limitation is that the sapling being cut often leans on the blade and binds it: if you cut on the side away from the lean this isn't a problem. The blade stays sharp wonderfully if you don't try and cut stones with it! Sharpenable with a 7/32 chain saw file.