Raspberry Pi 3B - Modep - CPU Load

I use MODEP with this simple setup on a Raspberry Pi 3 model B

I use it to play bass lines with my midi keyboard. I use hifiberry DAC 2.0+ audio card overlay.
It work nice and the CPU load is under 50% as raccomanded.

Now i want to add some other effect to the sound but i found that if I add some other plugin like cabinet simulators as in this picture

the CPU load increase to 60-70 % and i hear some artifacts. I wonder if this is an hardware limit because i user Raspberry Pi 3B or if is some wrong setup. What is the max complessity a pedal board can be using the Pi 3B ? Do i need to buy the Pi 4B with 4 or 8 Gb ?
Tnx for help

It’s difficult to say what the limits are - it all depends on the exact set of plugins you use and how demanding they are. In case there’s stability issues, try increasing the audio buffer size.

Of course upgrading to Pi 4 will improve the performance, I’d go with either 2GB or 4GB.