I do have a question on ensemble techniques Baggging/Boosting. - What would be the subset size for Bagging?
like said in a previous answer, the exact subsample parameter value depends on your data.
But a usual starting parameter that gets you good results in general, and doesn't hurt the data distribution much is 0.9.
Taking out 10% of your data at each iteration or newly constructed tree, makes your model generalize a little better. You can try out different variations of the 0.9 and see the results.
Bagging describes predicting based on the average result ob multiple models you created training on random subsets of data.
For example in scikit you can configure your Bagging models with
max_samples to tell him how many subsets to use. (see sklearn doc: https://scikit-learn.org/stable/modules/generated/sklearn.ensemble.BaggingClassifier.html)
If you're asking how high it "should" be, the answer is depending on your total volume of training data.