Hi Flavius,
1- To change font size of Hero - Tittle, you can use this custom CSS:
.acm-hero .hero-title {
font-size: 120px; /change to your desired value here/
}
2- This Sponsors module is JA ACM - Clients : style-1 module which doesn't support slide feature like that, unfortunately.
3- Meet Our 20+ Speakers: this module shows articles from category called 'Speakers' and it displays Intro image of each article which set via 'Images & Links' tab of each article: http://prntscr.com/ipx45r
4- You can change the title via Extra Field tab of each article - equivalent to a speaker.
Regards