I think we are generally approaching the issue from a wrong angle, at least for FireBolt and Acid Splash. What I believe based on the log is that Larian added 2 conditions (similar to blinded, paralized, etc) that are not in 5e:

- Burning - deals 1d4 damage when applied, plus 1d4 at the start of the creatures turn. It then ends, and can be re-aplied if the creature walks through a burning surface
- Acid - while under this effect the target suffers a -2 to AC

These conditions do not stack with each other. After testing and shooting 2 Firebolts at the same target on the same turn the target takes 1d6 + 1d6 damage from the Firebolt while the 1d4 is not applied the second time from the second FireBolt.

Similarly with Acid Splash, the AC reduction does not stack.

I do not want these conditions to scale with level and I doubt they will. Because 5e conditions don't scale up at higher levels and neither do conditions in DOS games scale.

Then we need to consider two things - A - do these conditions belong in a DnD game, and if yes, are they scaled appropriately. B - should cantrips apply these effects.

A:

I do think the Burning effects needs to be in a game. It baffles me that in a game where you have fire based spells, fire elementals and dragons spewing fire there are no consistent rules for burning things. Fire elementals, Wall of Fire, Alchemist fire, Oil, Create Bonfire, etc all apply persistent fire damage but do so in completely different way. Streamlining these I think is a good idea, and making them do 1d4 is appropriate.

The Acid effect I am not sure - doesn't make much sense to me. At least at a -2 to AC, if it were -1 then I think would be more reasonable, but I am not sure why it is in the game.

B:

Should cantrips be able to apply these effects. I think so. Whether FireBolt is a good choice - if it is scaled down. There is a Create Bonfire cantrip that would probably be a better candidate though. Perhaps make it do 1d4 fire damage on a dex save and apply a burning effect?

Acid splash applying the Acid status effect makes sense and I think it is ok. Maybe a reduction in area would be appropriate and a reduction of the cantrips damage to a 1d4?