Will I be able to hit level 60 in 1 go?

Very easily.

BioWare stated they tweaked XP system in ME1 in MELE in such way that you will be able to hit level 60 on first go.

The answer is probably buried somewhere in the Mass Effect Legendary Edition (General Discussion) thread, but it was stated that they tweaked the XP requirements so you could reach level 60 in a single playthrough. They also removed level 50 restriction for the first playthrough, and removed the XP penalty for killing enemies in the Mako.

There are two leveling systems you can choose in MELE:
- Classic Mode (levels 1 - 60)
- Legendary Mode (levels 1 - 30)

From what I gather for Legendary Mode, you gain XP at the same rate, but XP requirements are increased for each level, but you also gain more talent points for each level. Essentially, Legendary Mode removes about every second XP level from Classic, but gives you the extra talent points you would normally get otherwise.

I played ME completionist on insanity.

Reached LE level 28 (which showed as classic level 55) on the import save.

So there must have been some kill opportunities I didn't take, but I have no idea where.

I found some random clusters of enemies just staying in the empty parts of the map, away from any marker. Guess that's some extra exp.

Right now I am Legendary level 24 (at work, so going just by memory, at worse it's 23), did all possible side quests to this point and am starting Feros before going to Virmire. Rough estimate says it's not enough content to get to 30, unless the Exp rewards are higher at the endgame.

It's not possible from what I've seen/experienced.

28 on Legendary (level 55 in ME2 import) or 57 on Classic seems to be the max.

I missed some XP on my level 28 character (i.e. told off both reporters, didn't get alignment quest), but I'm not sure if it would have been enough to reach level 29, even less likely level 30 (I was still missing like 10k before triggering Saren's fight).

There's a bug so that even if you do another playthrough to reach '30', it hangs at 29 even when you go over the XP requirement.

Is that only when the Legendary level up scheme is used or is it hanging up below Level 60 in Classic as well?

From what I understand when you can get out of the Mako here and there and as a team defeat the ones you can  it seems  to have worked for me to reach 60.

They increased xp gained by 20%. Tested it via dev console.
Final level in both Legendary and Classic is bugged; when you reach xp needed for final level you don't level up. If you try to use dev console to give your self xp needed to level up from 1 to 60/30 you simply stay level 1 no mater what.

EDIT:
They actually didn't increased xp by 20%, they just enabled xp achievement bonuses from the start.
So it is impossible to reach level 60/30 in one go.

Do you get any XP bonuses for completing the game in the Legendary Edition (like the original), or no?
Perhaps it is just a matter of not getting to level 60/30 on the first playthrough, but then being able to do it on subsequent playthroughs.

I am unlikely to hit the max in my first Legendary Edition playthrough since I will not be getting the Paragon or Renegade specific missions. I am playing a mix of Paragon and Renegade, and not spending any points into Charm or Intimdate so I am not going to pass many checks. I will still probably stick a gun in Conrad's face for old-times sake.