I want to install Linux Mint 19.2 (Cinnamon DE). My laptop has a 96GB ssd plus a 1TB hdd. Of course my intention is to boot from ssd , so the '/' partition will go there, but here is the point: should I give it the full ssd space (so 96GB)? My idea was to reserve 40/50GB of ssd for the root and the remainent 40/50 for the /home partition, as I will be able to install some weight programs on ssd. Finally, the hdd will be reserved for storage and lighter programs (I'm quite new in Linux, maybe this is a more Windows-like approach). The alternative is simply to put / on ssd and /home on hdd. Which solution is the best?
Splitting a disk into partitions for different parts of the standard tree is a very old trick and one that probably does more harm than good on an end-user system where space needs can't be predicted very well. If you find one day that you want to install Android Studio or some other large software package to / and you've given all your space to /home, or need space to download an ISO image and all the free space is in / it will be a royal pain in the neck to fix. The simplest solution is not to split them.
If you want to experiment with this anyway I'd recommend using LVM to provision only as much space in each partition as you need now and leave the rest in the pool for later. That way when you need more space somewhere you just give the LV more space and resize the filesystem to use it. If you felt like living dangerously you could even add another disk to the pool and keep allocating.
The big exception these days is the EFI Sytem Partition ( or /boot ) partition. This needs to be a real partition (primary often on MBR disks) so the firmware can find it and for UEFI needs to be formatted FAT16 or FAT32 with the right type field in the partition table. Fortunately it doesn't need to be very large and a gigabyte or less should do the trick unless Mint is leaving behind way-too-many copies of the kernel and initramfs.