You have an Exchange Server 2016 organization named Contoso.
You create an organization relationship with a partner’s Exchange Server organization named Fabrikam. The
users in Fabrikam can view the free/busy information of all the users in Contoso.
You need to ensure that the users in Fabrikam can view the custom Mail Tips configured in Contoso.
What command should you run in Contoso? To answer select the appropriate options in the answer area
Hot Area:
Answer: 
MailTipsAccessEnabled
The MailTipsAccessEnabled parameter specifies whether MailTips data for users in this organization are returned over this organization relationship. The accepted values are $true or $false. The default value is $false.
MailTipsAccessLevel
The MailTipsAccessLevel parameter specifies the level of MailTips data externally shared over this organization relationship. This parameter can have the following values:
All All MailTips are returned, but the recipients in the remote organization are considered external. For the Auto Reply MailTip, the external Auto Reply message is returned.
Limited Only those MailTips that could prevent a non-delivery report (NDR) or an Auto Reply are returned. Custom MailTips, the Large Audience MailTip, and Moderated Recipient MailTips won’t be returned.
None No MailTips are returned to the remote organization.
The default value is None.
So if I’m not mistaken: If you just Enable Access – the default level is “None”, so no tips will be available.
My answer would be BOTH or better test it in LAB – if you Enable it works alone.
I would guess that the MailTipsAccessLevel All will be REQUIRED
This is what user Sam wrote on an older version of this question and I agree with him:
When you enable MailTips for an organizational relationship, the following recipient-specific MailTips are returned for all users:
-Automatic Replies
-Mailbox Full
-Custom MailTip
Thats why “Set-OrganizationRelationship Fabrikam -MailTipsAccessEnabled $true” is enough
Set-OrganizationRelationship Fabrikam -MailTipsAccessEnabled $true