When you refill a fixed order the ETA does no change (increase). All fixed orders have a 24hr max runtime no matter how much you are willing to spend. Plus, you cannot edit fixed orders from the Orders page.
Fixed orders are limited to max. 24 hours run while standard orders can run up to 15 days. Refilling of fixed order will change ETA, if it started initially with not enough BTC to run for 24 hours or more.
We received a lot of questions regarding remaining time and balance. A lot of customers complained that some orders are running for infinite time, because they were relying on remaining time too much (while in fact, other customers were simply constantly refilling their orders). We received requests from customers that wanted to hide remaining BTC on their orders from public views, so they could put in larger values (request for privacy).
When we opened Live Marketplace for beta testing (~2 weeks ago),
we received 0 complaints about remaining BTC on foreign orders not visible any more.
The viewable data about foreign orders is as it is and will stay.
Miners count is needed information, because order speed is always measured for the past. Miners count tells you ASAP which orders are receiving hashing power which is needed information to bid appropriately.
And for the end; if you would like to automate your bidding on NiceHash, we made NiceHashBot, which allows you to do that easily: https://github.com/nicehash/NiceHashBot