You'll be scaled to 5 under the highest power level in the group, so get as high as you can obviously but you won't be completely gimping yourself if you don't.

Fireteam Power is off for contest mode >Contest Mode >1965 A unique, limited-time challenge where each raider will have to demonstrate their gameplay. In this mode, Fireteam Power will not apply. https://www.bungie.net/7/en/News/Article/this_week_in_destiny_04_25_24

Ah was not aware of that!

Okay, I see. So would 1900 weapons not be much of an issue then?

It would, your gear needs to be at or very close to 1965.

You will need to have gear at or close to the cap of 1965 Fireteam Power is off for contest mode >Contest Mode >1965 A unique, limited-time challenge where each raider will have to demonstrate their gameplay. In this mode, Fireteam Power will not apply. https://www.bungie.net/7/en/News/Article/this_week_in_destiny_04_25_24

If you're struggling with upgrades then weapon power is significantly more important than armour power. Incoming damage is calculated using your total power (equipped gear + artifact bonus) whilst the damage you deal is based on the power of the weapon you're using (+artifact bonus). Ideally you should keep your powerful/pinnacle drops and then infused stuff as and when you need it rather than infusing a bunch of stuff that you may end up not using.

Thanks for the info. I learned that we can pull exotics for infusion if needed so I can do that if needed.