As a data point, my plan has both 401(k) contributions but is covered by 415(c) limits. I hit the max dollar limit in August. The company is still required to make their contributions, which spill over into a retirement health account.
So, for me:
max number - yes
catch up - yes
additional savings - yes
But here is the critical point: the preponderance of my portfolio comes from the growth of very modest dollar contributions invested decades ago.
Sure, I max it out now, as I have for a very long time. But the big investment numbers now are meaningless because this portfolio success is result of the actions taken in the early 1990s, when carving out $166/month from the budget for a family of four, living on one modest income, was hard, and took sacrifice.