Maxi-Cosi Rodifix is a very popular high back booster seat installed with Isofix. It's light weight, quite narrow with adjustment to grow wider, has great adjustable recline and the patented air filled head support.
Installation is done in seconds with Isofix and the seat can of course also be installed with seat belt only if needed. Recline is easily adjustable in two positions with a handle under the seat. Height adjustment is easily and smoothly done with one hand.
The seat is quite narrow but can be made wider to accommodate growing children. Simply push on the side cushions and with will be greatly extended.