compost: how much lower EC than coco?

[GreenBalls]

Hi all,
I currently have plants in coco, and I want to grow an extra one in a planter on my windowsill, just for fun/experiment/etc.

To use coco I'd have to buy a bag of coco, but I have a big bag of multipurpose compost sitting here.

Quick questions:
1. Is there any reason I can't or shouldn't use multipurpose compost indoors to grow a plant?

2. I use a loose EC schedule, with quite low ECs in general because I'm growing autos. As compost contains its own nutrients, does that mean I need to further decrease the feed EC, and by how much?

Thanks!