If it doesn't show on netgraph then it's not lag spike. Lag spike = your ping sky rocketing up for few seconds.
You might want to try and describe how does it feel, what happens during this 'lag spike'. Are the model players frozen? Do they move normally but you are frozen in place? Does your landing animation delay compared to normal? How often does it occur? At what occasions (fps drop on renoir, high speed ice, etc)? Enable cl_drawping, cl_drawfps, cl_drawpps, net_graph and sshot the screen when this 'lag spike' occurs and post it here.
Possible tests:
1) Reduce your fps to 200-400 - cl_maxfps
2) Turn on vsync and see if it helps in any way
3) Go to task manager and set paintball2.exe process priority to high
4) If you have nvidia post here your 3d settings (nvidia control panel > 3d setting > all these checkboxes), maybe you enabled sth by accidnt which causes these lags
5) Reduce your PB refresh rate if you have some gaming monitor the game might be running on 144hz, reduce it to 60hz (or if it is on 60hz, increase it to 144hz or w/e is your max hz rate of monitor)
6) Also, drivers up to date might not be the best thing ever especially for a game this old. Try downgrading few GPU drivers back, I remember I had to use driver which was 3 years old in order to not get BSOD in PB (in other games everything ran correctly, but lagged, since the driver was old)