Drums: all quantized and at the same velocity - definitely sequenced.
Bass: all quantized and also at the same velocity - definitely sequenced.
Keyboard strings: the only one that can be either played live or quantized. But does not really matter since one can record midi "live" playing into a sequencer with makes it sounds "live", but by definition, it is still sequenced. Still, I believe it is sequenced for a few reasons:
1. they also sound quantized (a bit more difficult to distinguish than the other instruments because of the decay)
2. the jarring high "G" was sequenced to fade off followed almost immediately by the C chord with volume adjusted to a higher level - definitely need sequencing to do that.
The difficult question to ask is: are the strings played or programmed note by note (both still defined as sequencing when recorded into a sequencer). My thinking is probably note by note programming because the chords are held at complete full value (4 counts). When played, we usually don't do that especially when the triad chords are in root position and jump quite a bit in intervals - unless of course you use the sustain pedal.