Creating a relatively small amount of particles at a high speed completely lags out the game (in 1.16 this doesn't happen).

How to reproduce:

Run 

particle smoke ~ ~ ~ 0 0 0 100 20

Which only creates 20 particles, at the speed 100.

Observe the game freezing (only for a few seconds, a higher speed lags it out far more).

I went through every particle available to the particle command using the above method; I got:

Particles which do this:

• Smoke
• Campfire Cosy/Signal Smoke (very severe)
• Large smoke
• Bubble pop
• Firework
• Fishing
• Item
• Poof
• Snowflake
• Soul
• Spit
• Totem of undying

Particles which don't do this:

• Ash
• Ambient Entity Effect
• Angry villager
• Bubble
• Block
• Barrier
• Bubble / Bubble column up
• Cloud
• Composter
• Crimson Spore
• Crit
• Current down
• Damage indicator
• Dolphin
• Dragon Breath
• Any dripping
• Dust/colour transition
• Effect
• Elder guardian
• Enchant/ed hit
• End rod
• Entity effect
• Explosion / emitter
• Falling *
• (Small/soul fire) Flame
• Flash
• Glow / squid ink
• Happy villager
• Heart
• Instant effect
• Item slime/snowball (not item itself, that lags)
• Landing *
• Lava
• Mycelium
• Nautilus
• Note
• (Reverse) Portal
• Rain
• Sneeze
• Splash
• Spore blossom air
• Sweep attack
• Underwater
• Vibration
• Warped spore
• White ash
• Witch