I'll answer this in two parts, Range, and the Spell
Any spell can, with one Reach, be cast at a target at Sensory Range (MtAw2e p112 "Common Reach Effects"). This does not let you cast at someone remotely, however. To do that, you would need Space 2 to cast at Sympathetic Range (see p173)
At Mind 4 you have a lot of options, including the Psychic Reprogramming spell (p164), which, among other things, states:
The mage may change one of the following aspects of the subject for each Potency of the spell: ...a non-Physical Persistent Condition
This means that you could inflict several very nasty conditions on them such as Broken, Fugue, or Madness (p314-316)
However, for a simple 'Nonlethally disable an opponent' spell in Mind, we can also look to lower Arcana spells. As you mentioned, Befuddle (p161) lets you reduce their mental or social Attributes, or Psychic Assault to deal bashing damage (although this can roll over into Lethal if they are already injured)
As another option, you could potentially create a Mind 4 spell via Creative Thaumaturgy to create a Weaving (Mind 3) or Patterning (Mind 4) spell to send someone to sleep, based off of Sleep of the Just (p162)
You will not be able to cast a spell at someone who is not nearby using only Mind, but spending a Reach to get Sensory Range will let you cast on anyone nearby.
Remember that you only get limited Reach before you start incurring Paradox, so it is less dangerous to use Mind 3 spells (As you mentioned, Befuddle is an option) so you can cast them Instantly and at Sensory Range without risking the horrors of the Abyss trying to eat your soul. However, Mind 4 opens up several potent options that are much more flexible (e.g. Psychic Reprogramming).