There are two types of exclusion. as far a I know in sequence. First, is per email and second is in global settings of sequence. To answer your question above.
do not change any "exlude filters", will it automatically send to all subscribers or do I have to manually add subscribers to the email sequence? - Sequence will not sent to your subscribers automatically. You need to use a bulk action or visual automation. I will attached some linked for you to read. This are helpful links.