Yep, dont target high hydration as you dont want holes but a fairly dense crumb. perhaps 600 ml of water per 1kg of bread. you can also use eggs and oil to enrich it. I think a Hhalla is a perfect sandwich bread for for a square loaf.
Personally I prefer buns for "portable bread" since they are easly frozen and defrosted in the morning to maintain freshness for 1-2 weeks.