Need Inverter and Battery help

Is sine wave really that important? I've seen conflicting opinions online about it for home use or even PCs, saying that it's only really needed for medical or lab equipment.

I decided to go with a simulated sine wave line-interractive UPS instead for my pc as line-interractive seemed more important?. Did I make a mistake?
It is highly recommended to get pure sinewave inverter for PC & other expensive electronics, not like the cost difference is too much to skip this. The output is considered cleaner but simulated sine wave will likely run fine provided the switch over time is low enough.

My friend almost purchased a Luminous 2400VA inverter but it was just not able to do the switch over fast enough for his LG C3 TV (it took over the PC load while gaming just fine). The seller later brought an Exide inverter (2000+ VA) which worked as expected.
 
My friend almost purchased a Luminous 2400VA inverter but it was just not able to do the switch over fast enough for his LG C3 TV (it took over the PC load while gaming just fine). The seller later brought an Exide inverter (2000+ VA) which worked as expected.
So the Luminous which he bought is not pure sinwave?