Applying Multiple Window Functions in 1 SELECT using different partition
That should be fine.

Your first column (LAG(salary)) will be calculated over the partition you specified, which the second column will be calculated over the second partition. 

Note that each partition specifies its own ORDER BY clause - so your windowed functions are calculated based on your row's position within the partition and its own order by clause.

I can't see any issues with this.

When you run it, do you get the results you expect?