Most of my FT8 QSOs are with 2.5W and very simple antennas. Although I own an FT-991A, I was considering trading this in for an IC-705. This ICOM radio runs 5W off the battery and up to 10W with an external PSU. This would be more than adequate for me. Most of my FT8 QSOs are with 2.5W and the FT-817ND.
Most of the time I use resonant antennas, so the internal auto-ATU on the FT-991A is not essential. Some worry about the extra loss in ATUs, but this usually just a fraction of an S-point. The IC-705 was going to cover 4m but no longer does on TX. It does not have an internal auto-ATU and is very expensive. Maybe later, when the price drops and the initial bugs are resolved.