The 1030 is still crap.
For comparison: With my GTX 970 I can run IL-2 1946 maxed out, as well as Battle of Stalingrad, but not quite Cliffs of Dover.
With a GTX 750 you can run IL-2 1946 maxed out, but might have to back off on Anti Aliasing settings in Nvidia Control Panel a bit. Battle of Stalingrad will run with medium settings, Cliffs of Dover... no idea. Probably just basic settings.
A GT 740 can barely run IL-2 1946 in perfect settings, but only if you disable all kind of Anti Aliasing and stuff. Battle of Stalingrad, Cliffs of Dover etc. in Fullscreen mode with reasonable quality: Forget it.
So that's the x70->x50->x40 line. Anything below that: No deal.
When you are talking about a 300W PSU, then I take it that the PSU has no 6/8 pin PCI-E connector to give additional power to the graphics card.
That's a quite common issue on smaller PCs.
The solutions is: Get an Nvidia GTX 1050Ti. It's the biggest bang you can get without additional PCI-E connectors, powered solely through the PCI-E slot, with a max. power consumption of 75 Watts.
To numerize it (Passmark values): GTX970=8575, GTX750=3284, GT740=1575. GT1030 would be 2285, GTX1050Ti is 5815. So the 1030 would be below FullScreen "good" threshold, the GTX 1050Ti is right in the middle between the "perfect" 970 and the "still good" 750.
Cheers!
Mike