No Mac sold in the last 5 years will slow down due to lack of memory just from the apps you are running.
If you are not tecky, then get the base standard configurations.
If you don't know about computers, then don't order optional upgrades.
If you want a speed improvement, upgrade the hdd to an ssd.
I installed an ssd in my last Mac but still had slowness after some time. I just think besides the ssd more ram would be a good option.