Carbon fiber masts work perfectly for inverted-V and sloped configurations, and are a lot shorter and lighter than fiberglass. We discussed this e.g. here:
For verticals, it will depend on the brand, but in my experience the effect will only be a slight detuning, not a a severe loss in efficiency. If you use a vertical with a rig with auto-tuner (like KX2/KX3 or MTR with T1), then I see no reason to go with the bulkier and heavier fiberglass mask. I have not used a fiberglass mast on any of my 20+ activations this year, only the 5m and 6m carbon fiber ones from DAM.
73 de Martin, DK3IT