Access to Chat and Files for Attendees Arriving Late

You can accomplish this by using Continuous Meeting Chat (CMC). But we need to make sure your intended audience are added as "members" to the CMC (as opposed to guests).  The setting needs to be enabled by your Admin and you should double check to make sure it's enabled for you. Then, once you schedule a meeting, it stands up a chat channel in the background.  Once one message is sent, it shows up for everyone in Zoom in Team Chat.
If they are internal users added to the meeting right when you schedule the meeting, then they are automatically members. If they are external, then you need to manually add them as member to the CMC chat channel after you send that initial message to activate the chat channel.  You can do that individually or copy/paste emails in bulk to add users.
Then you can send messages, files, links and pin those messages for everyone.  When they join the meeting, all members have access to chat before during and after the meeting.  Those considered guests will only have access to the meeting chat from the point after they join the meeting until they leave/meeting ends.
https://support.zoom.com/hc/en/article?id=zm_kb&sysparm_article=KB0058301 
https://support.zoom.com/hc/en/article?id=zm_kb&sysparm_article=KB0058605

You could add a banner with plain text and perhaps links that are displayed as a custom closed caption in the Zoom meeting (outside the chat) and are visible once the meeting has commenced. This can be done either using APIs or if you are not a developer there is a Zoom app, Salepager, that lets you pin a banner as a caption to the Zoom meeting.

Any thoughts on adding the ability as the "Host" to allow new attendees to see the past chats (before their arrival) in the current meeting or not? 

Useful when a number of key doc links are shared to start the meeting and someone comes in just a few min late and links are not visable (but most don't remember that is the case).