Free agent Williams, 28, is in the process of completing a move to the club after leaving Reading and turning down fresh terms at the Madejski Stadium.
Town are also working towards completing a deal to sign Derby winger Ince, 25, following positive discussions regarding a fee with the Rams and Montpellier striker Mounie, 22 - set to join for a club record £11m deal.
A fee was agreed with the Ligue 1 club last week to bring in Benin international.
But the completion of the deal has been delayed by the sad passing of Montpellier president Louis Nicollin, who died suddenly on Thursday, with his funeral due to take place today.
Town are also being linked with a move for Fulham left-back Scott Malone.
Middlesbrough have opened negotiations with Norwich City in an attempt to sign midfielder Jonny Howson.
Boro chief Garry Monk has identified the former Leeds player as his leading midfield target, with the 29-year-old expected to leave Carrow Road this summer.
Howson has rejected Norwich’s offer of a new contract and is keen to return north, with the Canaries ready to cash in.
Meanwhile, Leeds keeper Robert Green is being monitored by Boro and Sunderland, while young Elland Road custodian Bailey Peacock-Farrell is being linked with a loan move to Oldham Athletic.
Hull City winger Kamil Grosicki is being targetted by Newcastle United in a potential big-money move.
Manuel Garcia, also the agent of Magpies chief Rafa Benitez, has told the media in Poland that Newcastle could be willing to pay £10m for the 29-year-old, who joined Hull from Rennes for £7m in January.
Crystal Palace, Watford and West Bromwich Albion have also been credited with interest for Grosicki, with the Polish international reportedly having a relegation release clause.
Barnsley are keen on Reading striker Dominic Samuel, but Championship rivals Ipswich remain favourites to sign the 23-year-old.
Bradford City – who will receive a windfall following the £4.5 sale of Andre Wisdom from Liverpool to Derby - are expected to unveil Wimbledon midfielder Jake Reeves within the next 24 hours after agreeing a deal in the region of £150,000.
Portsmouth, Plymouth and Blackpool are being linked with a move for Sheffield United defender Chris Hussey.