Made informal and formal speeches

Hi. I think we can write "informal and formal speeches" to indicate that one informal and one formal speech. Could we then later reference them by putting the definite article in front of them?

He made informal and formal speeches to groups of college students last week. The informal and formal speeches
were received enthusiatically by the students there.

Also, if we modify the phrase "informal and formal speeches" with the adjectives "powerful" and "heart-warming" and in turn modify both adjectives with the adverb "very", could we put a comma between the adjectives "powerful" and "heart-warming" (instead of the conjunction "and") to indicate they are coordinate? Thank you for your help in advance.

He made very powerful, heart-warming informal and formal speeches to groups of college students laast week.