All spells and skills are based on the skill line where they are coming from. Therefore, if you slot a skill that is coming from Weapons > Two-Handed , you can use it as long as you hold a 2-handed weapon. However, if you slot a skill that is coming from your class skill line (e.g. Aedric Spear > Biting Jabs) you can use it with anything, since all it requires is that you are a templar.
Templars have a wide variety of roles they can support. They can be 100% stamina-based (using 2 handed weapons, dual wield, or bows) or go with the spells game style (hence, magicka users) as healers or magic damage dealers (restoration staves or destruction staves respectively). BTW, they are excellent healers.
At level 15 you can get the 2nd skill bar (and a 2nd weapon slot) so you can support a 2nd role, or enhance your main role. E.g. you can be a healer on slot 1 (healing spells, restoration staff) and a damage dealer on slot 2 (damaging spells, destruction staff). Or - if you choose the stamina damage dealer style - having a 2hand weapon on one slot and a bow on the second so you can have some range damage as well.
In ESO regarding character build, sky is the limit.
Also, make sure you get in the other 2 game guilds as well; Undaunted and Fighters guilds. They offer a skill line each, so it is useful to have them available.
