Can I match each client's preferred format?

Yes. You set the font, size, colour and weight for every text level, choose whether budget lines come out numbered or bulleted, and decide how much of the budget each table shows. Save the finished budget as a Workspace Template and the client's format comes back on their next job.

Set the type

Click in the page body so no table is selected, then open Document settings at the top right of the document pane. It opens on Design.
Under Document Font, start typing the client's font. The picker searches Google Fonts and shows each name in its own face. The font is embedded in the exported PDF, so the client sees it whether or not it is installed on their machine.
Under Text Design, pick a level tab, H1 to H4 or T for body text, then set Font Size, Font Color as a hex value, and Bold, Italic and Underline.
Each level is independent. Changing the font with H1 selected changes your top headings and leaves the other levels as they are.
Add Page Break starts every heading at the chosen level on a fresh page, which is how most submission rules want chapters laid out.

The same levels style the budget in a Classic Budget block: Section headings take H1 to H4 by nesting depth and Cost Item lines take body text, so one set of choices dresses the whole page.

Set the numbering and the detail

Click a budget table, then Settings on the blue frame.
On a Classic Budget, Cost Item Style switches between Numbered List and Bullet List. That is where line-item numbering comes off.
Show Heading Levels decides how deep a table goes. Set it shallower for a client who wants chapter totals rather than intermediate subtotals.
Show Cost Items, Show Prize per Cost Item, Hide empty Cost Items and Hide empty Sections trim what is left.
With a table selected, Design becomes Table Design. Style the table text from Cells and Header.

Carry it to the next job

Open the menu in the budget header and choose Create Template. The Offer Document attached to the budget travels with the template, so the typography, the numbering and the table settings all come back on the next job. Keep one Workspace Template per regular client, and their format is one click away for everyone in your workspace.

Good to know

Bullet List and Numbered List belong to the Classic Budget. The Cost Overview table is numbered to match the budget.
A budget made from a Workspace Template starts in EUR and In Progress, so check the currency on the first job you start from it.
The text you write yourself is headlines and paragraphs, so a client who wants terms as bullet points gets them as short paragraphs.