In general as your lookup tables get larger they’re going to have a larger impact on training and evaluation time.
This blog post is a little older, but it does provide some benchmarking numbers around performance for different size lookup tables: Entity extraction with the new lookup table feature in Rasa NLU
With 100k elements you may experience a slightly longer evaluation time. The biggest impact will be in training your model. You’ll likely notice your model is taking longer to train with 100k elements in your lookup table.