If I kill a yellow Viktor alongside two other units with Bellows Breath + Watcher, does the Viktor still get to spawn 2 recruits assuming the units that died are non-recruits?

No. Viktor will not spawn any Recruit tokens.

When Viktor and the other two units die simultaneously from the same damage event, Viktor leaves the board at the exact same time as those units. His triggered ability requires him to be on the board immediately after another non-Recruit unit dies to trigger (Rule 383.2.c.2). Since he's already in the trash at that point, his condition can never be met — regardless of whether one, two, or a dozen units die alongside him.