I did a couple of trips last friday in 755410 & took some pix of the interior, the driving cars (at least) have glass luggage racks above the seats. As for noise, they're quietest when sitting near the 1st & last articulation joints, (except on jointed track....) but I feel that the engine noise is quite obvious near the power-pack, especially when departing & in "cruise-control" mode, it's noticeably power on then power-off to keep to the desired speed.
The cruise control on my car seems to hold the requested speed on level roads with no noticeable variation in engine noise.
I'll have to watch the power meter to see if there's much variation when in cruise mode.