So I'm thinking of trying this list out
Elrond in heavy armour on horse 180pts, leader
5 Rivendell knights with shields
290pts

Glondindal in the Armour of Gondolin on horse
12 High elf warriors, 2 with elven blades, 4 with elven bows, 6 with shields and spears
280pts

Captain of Arnor with shield
12 Warriors of Arnor
151pts
total:721pts
I'm not sure what to do with the remaining points, atm I'm thinking of giving the High elf warriors with elven bows spears as well, and then either swapping one of the warriors with elven blade for one with banner and shield, or swap the captain of Arnor for Malbeth the seer or maybe just take a ranger of the North, thoughts?

I am also trying to go for a similar theme to my force with Arnor and Rivendell Elves.

I feel the main issue with your force is the low model count and the low bow count.
I would say this is due to having two large point heroes in a 750pt force. Some people make it work however I prefer lists with one expensive fighty hero, and then cheaper heroes to lead the other warbands.
Just tried making a similar list but with only elrond instead of glorfindel. You could choose to take glorfindel instead and replace elrond with an elf captain on horse.

Elrond in heavy armour on horse 180pts, leader
5 Rivendell knights with shields
290pts

Captain of Arnor with shield
12 Warriors of Arnor
151pts

Halbarad Dúnadan
4 Ranger of Arnor with Spear
101pts

Erestor
6 High Elf Warrior with Shield; Spear
2 High Elf Warrior
4 High Elf Warrior with Elf Bow
208pts

That is 750pts on the dot. I am no professional gamer and this list could suck, but after doing a little research of my own when trying to build a similar forces this seems like a reasonable list in my opinion.
Somebody who plays more regularly than me though may disagree.

In this list you've got 37 figures, one expensive fighty hero, two cheaper named heroes which are also pretty good, and just a regular captain.
You've then got a bow count of 9 as well, which is still pretty small but may be enough.

Main problem with that is that 4 of the those bows are only regualr bows, which I've found you have to take in bulk to work, not sure there is the numbers for them.
The point about the numbers is fair, but I'm hoping the toughness and speed of the troops I have should help, plus I've found one big hero is countered fairly easily, but two is usually enough to split an opponents forces.
Edit:I could always drop either one of the big heroes for more rivendell knights, the question then becomes which hero and do I try and fit a banner in the force as well.