Histograms in Machine Learning
I would suggest you, other than simple histograms, to visualize how variables are associated with each other using a pairplot from seaborn.pairplot(). This will let you check how correlated your explanatory variables are with each other. Multicollinearity can be a problem that you can solve using dimensionality reduction, for example.

Outliers might not be a problem, but you can't say before running any model. On that, I suggest you to run the same model more than once, with and without outliers. Also, always normalize your data, this might affect the "outlierness" of an observation.