If you want to maximise stealthiness, the Deep Gnome is the best racial choice.
Apart from that, all you need is proficiency, later upgrading to expertise, in Stealth and Slight of Hand, and a good DEX. So Bard is fine, no need to multiclass.
The College of Valour doesn't allow expertise in Stealth or Sleight of Hand in EA, only The college of Lore (and we don't know about College of Swords).
Rouge 1 Bard 3 does then give you expertise in 4 skills at level 4 so if you want a non-lore college and expertise in stealth and sleight of hand this might be the way to go. It just depends how whether you want a more martial bard or more of a caster staying out of the way sort of bard.