is there any way I can have the higher resolution without putting load on my MacBook?
More pixel density = more GPU load
Unfortunately, you can’t increase your resolution without “paying” for it. The higher the resolution, the more 1s and 0s need to be crunched by the GPU. The more the GPU has to work, the higher the power draw (more electricity). More power equates to more heat which means your Mac requires more cooling. Thus, the fans spin up (faster) as necessary.
It’s also not limited to spinning up fans. The CPU and/or GPU could be throttled (performance limited) so that it won’t draw as much power keeping temperatures at reasonable levels.
Size your gear accordingly
You never mentioned (in the original post) what particular MacBook you had nor what it’s specifications are. However, it’s likely it wasn’t sized correctly for this particular application or your expectations weren’t aligned with its capabilities
This particular 2019 MacBook Pro would have no issues driving your external monitor at the scaled resolution due to its dual GPUs and plentiful and quick 8GB of VRAM.
It’s a far cry from the entry level 2019 MacBook Pro with only integrated (with the CPU) GPU and VRAM which is shared with system memory. This model would struggle to drive the external monitor at the scaled resolution.
Please note: I opted to use an Intel rather than a Silicon based device because its easier to conceptualize this architecture versus Apple’s new one. While extremely graphics efficient, the Silicon chips don’t have a discrete GPU as they are integrated.
