After some research online, I'm finding conflicting information about this rifle. I'm still wading my way through what works, what's great, and what's crappy on different weapons, and people seem to think Efrideet has pretty decent impact.

I'm not swimming in weapons, but I do have a couple of maxed out LDR5001s (void, and arc) which I love. I guess this would be for PvP, maybe PvE… like I said, just not sure. Are these mods keepers, or should I roll, and if so, what mods would I be looking for?

Thanking you in advance.

I would re-roll to have, ideally, Field Scout and Armor Piercing. Both of those serve you very well in PvP, but if you roll Field Scout, that'll do. Double Down simply isn't very reliable, in my experience, and Final Round doesn't make a whole lot of difference in Crucible. Also, a Stability perk would probably help, but given the slow rate of fire, it might not do a whole lot.

Also, the Impact rating on that is crazy, so it's a great option for PvE as well.

I suggest DestinyDB.com to help you decide what rolls to look for. It'll show you what is possible on each weapon - as each one has slightly different groupings and possibilities.

Here is Efrideet's Spear.

I have a Void one with the 'Terrible Trifecta' of 'Spray and Play' (fast reloads when empty), Armour Piercing Rounds (Shoot through stuff) and 'Final Round' (extra damage on last round in mag).

The special thing about Efrideet's Spear and Final Round is that it's impact is so high, the final round is a one shot kill. Only a couple of other snipers in the game boast that ability. It's entirely possible to use it just for that and waste the first 2 rounds in your mag every time you reload.