I bought a Legion Slim 7 in 2023 and was gifted the Legion Slim 5 by Lenovo in 2024. Both are AMD Ryzen 7 powered with RTX4060 Mobile graphics.
The Slim 7 has a 7840HS and the Slim 5 has the 8845HS, the both have 32GB DDR5-5600 installed and came with a 1TB nvme. I put a 2TB WD_Black SN850X in the 2nd slot of the Slim 7.
The other difference between them, the Slim 7 has a 3200x2000 100% DCI-P3 165Hz panel and the Slim 5 is 2560x1600 HDR400 240Hz. The Slim 7 has per key RGB and an alloy chassis whereas the Slim 5 is white backlit and ABS apart from the lid which is alloy. And the battery in the Slim 7 is 99.9Wh as opposed to 80Wh in the Slim 5.
The perform very similarly in games, I use the Slim 7 for work mostly and get a full day's work out of a single charge still