There is no issue specific about this point, si I make one to add more details.
I'm playing in ultralowdetails (same for 1.2.4). It appears that lag spikes are occurring less often in this version. I would say like 50% less. Which is cool (but still too often compared to the original version, where I had none ^^)
That said, lag spikes are also a little bit shorter in duration, but frame drops looks bigger. I don't have precise statistics, but it's even more unplayable during these spikes than in 1.2.4.
Hope this could help you solve the problem! If you need more info, don't hesitate to ask me