The only laptop I'll buy is a ThinkPad. They are almost bulletproof. I'm still using a 2002 model on stage.
I can't give you details, but I always go for the biggest HD and the most RAM they offer. These are the kinds of things you can't have too much of.
Insights and incites by Notes
Lots of good tips here, but I'll add a +1 for Lenovo ThinkPads. I'm on my second one now (a P17) and love it.
An additional point to consider.
Expansion I/O ports.
Get as many as you can afford. If possible, select a laptop like my P17 that offers an I/O expansion. Mine connects via Thunderbolt3 and includes USB, HDMI and other kinds of ports.
In the music world, ports are gold. Audio interface. MIDI keyboard controller. External SSDs. MIDI foot controller (like the Behringer FCB1010).
My specific suggestions: 1) the fastest CPU you can afford, 2) at least 16 GB for RAM and 3) an external SSD for BiaB and other instruments and samples. With an external SSD, you can get away with a 500 MB internal SSD.
On my P17, I have a 1 TB internal drive and 3 external SSDs: one 2 TB Thunderbolt3 SSD for BiaB and other VSTi instruments and their samples, and two USB3.2 2 TB drives, one for work files and one for backups.
A basic laptop with a 500 MB internal SSD and one 2 TB external USB 3.2 (make sure the laptop provides USB 3.2 support!) for BiaB would be a great place to start. Or finish.
I use Samsung external SSDs. Check out the Samsung T7 USB 3.2 drives. They're about 9x faster than a high speed spinner. A 1 TB T7 is $120 and a 2 TB T7 is $220.
Samsung T7 1 TB Samsung T7 2 TB