differences among amd64 and i386

[fuf <fuflono@gmail.com>]

Good day!
Near a half month ago I bought a comp. made into 2011 year and didn't knew which Debian12 to put: i386 or amd64?, chose i386 as thought that old comp. didn't take amd64.
i386-netinst Debian 12 was being installed perfectly,  and later I could to read a disk owned to the comp.:
CPU
Support Processor Intel Sandy Bridge (Dual core / Quad core) (optional)
TDP 35W / 45W
Core Chips
PCH Intel® HM65
Memory
Technology
DDR3 1333 MHz
Memory DDR3 SO-DIMM X 2 slots
Maximum 8 GB
In BIOS I had read:  Memory 2GB,  Processor Speed  ~2GHz,  Disk 320GB.

I installed amd64-netinst Debian 12 but the bare base (for speed) hoping after  to add  all necessary. Of course nothing  couldn't . Third time I have installed Xfce and all to be suggested.
Now comp. is having  3 Debian 12 and 1 swap partition 4GB.
I  don't notice differences among amd64 and i386 but think to pick among this. Give advice, what better please? I will add memory if the spare slots are, but maybe all busy? There are 2 slots only.
 Also, is there any simplest way to increase the font at the "bare base" at once after login?
Thanks all.
--fuf